Infinitely variable gear



June 7, 1960 E. woYDT ET AL INFINITELY VARIABLE GEAR 5 Sheets-Sheet 1Filed Feb. 11, 1959 5 mx a? 7 V N. I ,A wv Q nl QA .Q Qr\\/ .www :ll wwNW9 ilfmwmm. m m H w k, f wmv Seu w u. w b Hnml IMVIIII lill! nw A LAum. Y m R Q R K@ w| NCQ I Q, A r www e S mi n, I Q\\r MN .mw WN k G v-FQ M .NT 51N \m. R7 /NZ/ NN buv m,

June 7, 1960 E. woYDT ETAL INFINITELY VARIABLE GEAR 5 Sheets-Sheet 2Filed Feb. ll, 1959 `fune 7, 1960 E. woYDT E'rAL INFINITELY VARIABLEGEAR 5 Sheets-Sheet 3 Filed Feb. l1, 1959 yal@ uff

June 7, 1960 E. woYD-r ETAL l 2,939,342

INFINITELY VARIABLE GEAR June 7, 1960 E. woYDT ETAL 2,939,342

INFINITELY VARIABLE GEAR Filed Feb. 1l, 1959 5 Sheets-Sheet 5 FIG. /2

TABLE GF 5495505 k L k L K K l q m l o L\ l n %*'Sn'uw uw q V) "I '0 '00 2000 2000 2000 2000 2000 o 2000 /550 0 0 k 2000 /525 -5200 -3900 /2702000 000 0 0 g 2000 005 +3200 -0040 2000 0 +2050 0 -1050 /NVENTOR Lino50017 J .Ha u/f M1-0% 07m/Qs.

United States Patent O INFINITELY VARIABLE GEAR Eduard Woydt, Stuttgart,and Alfred Haul, Kongen, Wurttemberg, Germany; said Hauff assigner tosaid Woydt Y Filed Feb. 11, 1959, Ser. No. 792,555

Claims priority, application Germany Mar. 12, 1958 2 claims. (c1.vtt-.687) f The invention isV in respect of an innitely variable gearwith a fbranch-o of the output into infinitely variable-for example,hydrostaticbranches and into` invariable branches. The invention isintended more particularly for motor vehicles and railways where theprime mover-for instance a diesel engine-shall run at equal engine speedin -all gear positions.

Since the eciency of the infinitely variable branches of the gear,particularly when they are equipped with hydraulic transmission unitssuch as pumps and hydraulic motors, is inferior to'V that of invariablebranches which are designed as toothed-wheel gears, the invention hasset itself the task of keeping as small as possible that part of theoutput which is transmitted via the infinitely varia- 'bleY units atvarious speed gear positions. This part is in fact to be smallparticularly at those speed-gear settings at which the vehicle is mainlyoperated. In accordancewith the invention, the thing that is to beachieved is that such a small portion of Ythe total output shall rbetransmittedY via the innitely variable-eg. hydraulic-units, that, evenin marginal positions and at part-load where the `efficiency of theseunits becomes very poor, the overall etiiciency shall nonetheless stillremain at the level desired. In addition, by alternately using theinfinitely variable as driving member or driven member, the hydraulicunits especially as pump and as motor, the constructional size is keptsmall. What is more, the switching-over of the infinitely variable unitsreferred to from a driving function to a driven function or vice versa,particularly from pump to motor, or vice versa, isperformed -free ofshock and without any intei-nal acceleration during the speed-change,:by transmitting the drive via planet wheels;

A further aim of the invention is to design the gear in such a way thatthe infinitely variable units, especially pump and hydraulic motor, aremounted stationary and do not rotate as a complete entity about a shaftin the gearing. One last aim of the invention is to make do on as smalla number of infinitely variaJble units as possible. In fact, with twosuch inlinitely variable units, each having'only a smalltransmission-ratio range, the invention succeeds in covering the gearsentire working range.

The invention consists in the fact that the drive is rst of all branchedolf into at least three sets of planet wheels whose common second memberacts direct on the -drive shaft, whilst the third member of at least twosets l 2,939,342 Patented June 7, 1961) ICC able gear with outputbranch-01T into mechanical lines' and with two hydraulic units workingin the Huid-circulation system. With such gears an appreciable advanceis achieved along the lines laid down in the foregoing remarks, by meansof a switch-over mechanism for the mechanical lines and/or a shiftmechanism yfor the active members (swash plates or eccentrics, forexample) of the hydrostatic units such as, when the pitch range of theentire gear is traversed, change over the hydro@ static units once atleast from pump to motor or from motor to pump (i.e. one unit from-motorto pump and the other unit from pump to motor). i

The invention will now Ibe further described with reference to theaccompanying drawings in which;

Figure 1 shows a longitudinal section through the gal;

Figure 2 shows a section along line IL-II koflFigure 1;

Figure 3 shows a section along line fill-'III of Figure 1; Y

Figure 4 shows a section along Figure l;

Figure 5 shows a section along line V-V of Figure 1;

Figure 6 shows a section along Iline VI-VIof Figure 1;

Figure 7 shows the developments of the controller cylinders (42, 43, 54and 55);

lFigure 8 shows a diagram of the gear;

Figure 9 is a curve showing the hydraulic output NHs share of the totaloutput transmitted by the gear, plotted over the adjustment range i;

Figure l0 shows the curves of the stroke volumes (V) of the twohydraulic units over the adjustment range i, with P denoting the way inwhich a hydraulic'unit works as a pump, and M the way a hydraulic unitworks as a motor;

Figure 11 shows the cylindrerablock speed curves NH over the adjustmentrange i, the one direction of rotation ibeing plotted beneath the zeroline and the other 'direction of rotation above the zero line;

Figure 12 is a speed chart.

A housing 1 (Figure 1) has a partition wall 4 and lids 2 and 3. IIn Ithelid 2 the driving shaft 5 is mounted. On it are firmly seated an inputpinion 6 and a drum 7 which carries an internally toothed input gear-wheel 8. The driving shaft 5 is mounted with its right end in thedriven shaft 9. lt is intended inter alia for this gear that, with thedrive shaft 5 running at a constant speed the driven shaft 9 shall lbesteplessly accelerated from stationary to top speed, as is in factdesirable as regards motor vehicles for example.

The shaft 9 is mounted for its part in the lid 3 and it carries a planetgear wheel supporting means in the form of a casing comprising a plate10 screwed on to a drum 11. The latter carries a wheel V13 with internalteeth and, with the aid o-f screws 11a, an inner walling 12, and it hasa wall 14 on which are located three bosses 18 forming bearings for aset of three identical planet gear wheels 18, and three bosses 16formedV as bearings for two similar sets of planet gear whee1s21 and 22,three segments 15 (see also Figure 6) which are welded on to the wall 14carrying a second wall 85 which form further bearings for the spindlesof the planet wheels.

On each of three planet wheel spindles 17 is seated a planet gear wheel18 which is in engagement both with the internally toothed input gearwheel Sas well as with a central pinion 25. On three planet wheelspindles 19 are mounted, on the left-hand side, toothed planet gearwheels 22 which are in engagement with ,anY internally toothed centralgear wheel 23. In the middle of each spindle I9 is seated a toothedplanet gear wheel 21 which ries, on Vthe left, a gear wheel 31 kwhichmeshes with a toothed. wheelf32..V Aff central pinionY 25 is mounted ona hollow shaft 27 which carries, Yontheleft, a. toothed wheel 30 whichVmeshes with a toothed wheel 34. Toothed wheel 23 isinounted on thehollow shaft 28 which, on the left,. carriesv a. .toothed wheel. which.meshesk with a toothed wheel 33 VThe toothed wheel l13gisy inengagement withfafto'otled casing drive pinion 35.@ The housing 56'ofone hydraulicunit Bhasa .shaft 36;:V the hous ing 5,7 of anotherhydraulicunithasa shaft 37.- The.

housings 5.6and57. are secured in thehousing 1 and carry lids, 7.5.(Figure 4.)! V011.th.Answer transmissin Shafts 36 and 37'ke'yways 80andy 79 respectively reiitted, on which sliding gearshiftlsleeves 3&arid are seated.Y Byturning controller cylinders 42Y andw43, levers'40and 41 engag-ing in curved, slots in theA controller.y cylinders YareVsi'vvivelledVV about their Vstationary axes 44 `and .45,t nas ares`11lt0 fWhichrthe` levers movel the .gearshaft sleeves 38 and 39 insuchaway that their jaws orne into engagement with `jaws oftheadjacent-gear wheels 32, 33, 34 and l35 respectively thereby couplingthese to thev shafts 36 and 37 respectively.- Y Y At'its left-hand end71 the shaft 37 is'irmly connected tothe cylinder block 72 of thehydraulic unit A,Y whilst, on the'rightihand side,V it is mounted in thepartition Wa114. s Y Y There isY a corresponding arrangement in respectofthe Vshaft 36 of the hydraulic unitB. Y

The cylinder block 7 2 isfrnoiinted in the housing V57 via a rollerbearing 73. YThe roller bearing. 73'has a cage 74 (see Figures llan'd3)'.

In the housing 57, on thelef-t, is seated a half-cylinder @'Which,fwith'a spheiicalfshaped lug 63, projects into aV recess 62 of anadjusting bolt 61 (Figures l and 5).

By turning a controller cylinder SSwhich is seated on ashaft ,47Yjointly Ywith theV controller cylinder 43, a rotatable/toggle lever 58inthe housing S7 is swivelled about` a bolt 60, as, av result of whichthe adjusting bolt 61 is moved up and down over the pin 59 and swivelsthe half-cylinder 64 via therball 6,3.. A spring 7G in Vthe cylinderblock 72 pressesVY the latter against the cover 75 Y ofthe hydraulicunit, and the pinA 69 against the re-set plate 68A. vThe latter, viarings 67, presses on cups 66 on the pistons 82, The cups 66 bear, by wayof attened Vhalls 65, against,v the half-cylinder 64. With their tlatsurfaces the lballs slide on the half-cylinder 64 and, with theirsphericalV surfaces, they swivel in the rings 67. Figure 2 shows there-set plateY 68 with its slits for ve pistons 82 and' the rings 67lying n nder'same, which are able to slide radially on the re-set plate68.

Figure 3 shows five cylinder bores 72a with their inlet and outletopenings 72b which, while the cylinder block 72 is rotating, strokealternately over the semicircular recesses 83V and 84-fshown in dottedlines in Figure 4-of the housing cover 7S serving as level of control.The rece`ss84 is in communication with a ring conduit 76 and the recess83 communicates with a ring conduit 77. Fitted on the ring conduit 76 isa topping-up pipe 78.

Mounted in the housing 1 is a control shaft 52 which can Abe actuated4via a crank 53 andV which, via helical 'gears 5,1, 50, rotates theshaft 4,7.with the controller cylinders 55 and 43 and, 'via helicalgears 49, 48, the shaft 46 controller cylinders 54 and 42.

Y When the coupling sleeves-38 and 39-are in the middle position, i.e.in engagement neither on the right nor on theY left, as shown' in Figurel, thegear is unable Ytoftransnrit, any power and the drive shaft S VisableV to rfotate'urtter freedom. ATo start up the driven shaft 9.

as from a stationary position, the coupling sleeves 38 and 39 have to bebrought into engagement to the 'right as is the case in Figure 7 atzero. The curves 55a, 54a, 43a and 42a are the developments of thecurved .slots in the controller cylinders 55, 54, 43 and 42.

As far as the gures are concerned, it is as well that the followingpoints Vshould be noted right from the outset: Figure 9 shows that thehydraulic portion of the output is very'small for 3A of the Atotaladjustment range i, in fact at three points 100,101 and'102, it is niland 1t only rises to about 40% in a very small and littleused workingrange at point 103.

Apart from very good overallefliciency over -a wide working range, smalldimensions are achieved 1n the hydraulic units. At point 104 Vthereduction is infimte, i.e. the vehicle speedV is equalA to nil- InFigure 10 the stroke volumes of the hydraulicl umts A and B are plottedupwards ofV` the zero line,wh1lst in A' Figure 7 the developments'of thecurved A'slots '55a `und 54a of the controller c 'linderfs 5K5 and 54'are plotted. A The deviations' of the curved slots 54a Yanti 5 5afrornthe zero f line (Figuref7) correspondito thefstrokeQvolumesjasper Figure10. The starting-up:operation v,from 104 -to 103 is explained'below withreference tothe Figures 1 0, 1l, 25V

8 and 7. k For a 'calculated exampleincwhich `the 'drive shaft 5 ispowered by a'motor with a constant speed ofA 2000 r.p.m., thespeeds vofthe shafts 136,377,267, yand 28 are summarised in a speed chart inFigure 12.V The speeds of theshafts36 and 37 are Ventered in Figure 11in brackets;` The speeds of the driven 'shaft 9 are plotted Vin Figure 7,as abscissa values.

YIn Figure 8 the halfcylinder 64, with the driven shaft 9 stationary, isin the nil stroke position shown in dotted lines.V If'the hand crank 53isf turned, the control slots in the controller cylinders 54 and 55acton the levers (eg. 58) in a manner such as is, shown byv-the curves54ar and 55a in Figure 7 from point 127 Ato 126 as well as from point133 to 132. With the shiftensuing herefrorn-of the half-cylinder 64'inthe directionfoflthe arrow, the unit A begins to work as apunip,The'strdke is increased in accordance with the curve 109 to 1,08 ofFigure 10. The stroke reaches its maximum at point 108 and Astays atmaximum until point 107 (rd'otted curve)'." At thesame time thecontroller' cylinders 42 Vand V43 are turned, the levers 40 and 41 notlbeing. swivelledright away however (.cf'. Figure `7 curves 42a and l43,right-handV side); As can be seen from Figure 7 curve 43a,thecouplingsleeve 39 has to bein engagement with gear wheel 33 rightfrom ythestart. l

In the course of all this, ithepower ow in the mechanical portion of thegear runs, cf. Figure 8, from the drive shaft 5 via the gear wheelsY 6and 20 on to the dotted-line shaft 19 via the gear wheels 22, 23, thehollow shaft 28, via the gear wheels 29 and 33 on tothe shaft 37.

By way` of the shafts 19 there is already a'power'. output branch-offvia the drum 11 on to the drive-off 9.

The other hydraulic` unit B works as per the dotted linedcurve 113, 108,112.(Figure10) asa motor,.its halfcylinder being moved from the'positionplotted -in dotted lines in Figure 8 towards the zero position. Thistakes placeY (Figure 7) according to the'curve 54a from point 133`to 132by virtue ofthe Ifact that thej controller cylinder 54 causes :acorresponding rotation of the/halfcylindeff Because ofithis, the ow ofApower, as; per Figure 8, passesaccording to the dot-and-dashr line' fromthe shaft V36 via the gearwheels; 35 kand 13, on tothedrive-.ot 11, Y9.This isrrrenderedpossible'byvirtue of thefacty that, nas can be seenfrom Figure 7= curve 42athe coupling 0.11.1131? righti With gear whilstthe hydraulic unit B. of the shaft 36 is working as amotor. Y

'Ihe vehicles internal combustion engine should at all times be runningat a constant speed (n=2000 r.p.m.). At the time of starting up,thespeed of ,the shaft 37 is equal to the section 121 to 117 of Figure11'. Since the half-cylinder 64 is then in the dotted-lined nil strokeposition, no power is able to pass through the gear. It-is not in factuntil the half-cylinder has been brought into deflection in thedirection of the arrow that starting-up actually -begns (see also thebottom chart, Figure 12).

The starting up operation is terminated at point 103 of Figure 9.Despite this, the speed of travel continues to increase from point 103to 102 since, in accordance with Figure 10, by lfurther turning the handcrank 53, t-he stroke volume of the unit B, working as a motor, isreduced from 108 to 112 down to zerd, Whilst the stroke volume of theunit A, working as a pump, stays constant from 108 to 107, therefore thehydraulic unit B working as a motor, must run faster and consequently,the vehicle must do so too.

At point 112 in Figure 10 the stroke volume of the unit B working as amotor is nil, i.e. the half-cylinder is in the zero position whereas thespeed of the shaft 36 of the unit B has reached -a maximum at point 120in Figure 11. The toothed wheel 34 now has exactly the same speed as theshaft 36. (This is the result of the corresponding dimensioning of ltheset of planet wheels 8, 18, 25.) Since, apart Afrom this, the strokevolume of the unit B is nil at this point, i.e. there is no torqueacting on the shaft 36, the coupling sleeve 38 can now easily be broughtinto engagement with the gear wheel 34.

From Figure 7 can be seen that, while the coupling Asleeve 38 is beingpushed over, the stroke volumes of the two hydraulic units A and B stayconstant, therefore no alteration of speed takes place during theswitch-over.

The drive-olf speed stays all the time at approximately 665 r.p.m.

The flow of power occurs after the coupling sleeve has been pushed overas per the dotted lines in Figure 8, i.e. from the drive shaft via thegear wheels 8, 18, 25, on to the hollow shaft 27 and via the gear wheels30, 34, on to the shaft 36. The hydraulic unit B functions as from point120 of Figure 11 as a pump, for the simple reason that the otherhydraulic unit A at point 116 in [Figure 11 has changed its direction ofrotation, passing through zero in the process. This change of rotarydirection is brought about by virtue of the fact that the dimensions ofthe set of planet wheels 6, 20, 22 and 23 are so selected that at thisspeed-ratio of drive shaft 5 to the drive-off shaft 9 the speed of theWheel 23 is nil.

According to Figure 10 the unit B functions therefore as a pump frompoint 112 to 111, and, from point 107 to 106 the unit A functions as amotor. -In order to increase the vehicles speed further, by turning thecrank further the stroke volume of the unit B working as va pump is nowincreased corresponding to curve 112 to 111 of Figure 10, and that ofthe unit A working as a motor is reduced corresponding to 107 to 106. InFigure 7 this corresponds to the curves 131 to 130 and 125 to 124. Atpoint 119 of the Figure l1 the speed of the unit B working as a pumpbecomes nil as a result of the corresponding dimensioning of the set ofplanet wheels 8, 18, 25, and, just as at point 115 of Figure 1l, by acorresponding dimensioning of the gear wheels 6, 20, 21, 24, a state ofaffairs is achieved in which the gear wheel 32 rotates at exactly thesame speed as the gear Wheel 33 or the shaft 37. The coupling sleeve cantherefore easily be brought into engagement with gear wheel 32 moreparticularly since the stroke volume of the unit A working as a motor isnil here (point 106 Figure l0), therefore no torque is transmitted bythe shaft 37.

Because the hydraulic unit B has changed its direction of rotation byway of neutral, as from point 111 to 110 column of the speed (Figure l0)the unit B againl works as a motori and, as from 106 to 105, the unit Aagain works as a pump.

It can be seen from Figure 7 that, again while the coupling sleeve 39 isbeing pushed over, the stroke volumes of the two hydraulic units, and,consequently the drive-oli speed, stay constant =-1525 r.p.m.

. yThe flow of power takes place when the crank 53, after thefcouplingVsleeve 39 hasbeen pushed over, is turned further still, correspondingto the dash-and-cross lines in Figure 8, i.e.,fromthe drive shaft 5 viathe gear wheels 6, 20, 21, 24, the hollow shaft 26 and the gear wheels31, 32, on to the shaft 37. By turning the hand crank 53 further still,the stroke volume of the unit A working as a pump is increasedcorresponding to 106 to 105 of Figure 10, or 123 to 122 of Figure 7respectively, and the stroke volume of the unit B working as a motor isreduced corresponding to 111` to 110 of Figure 10 or 129 to 128 ofFigure 7 respectively, so that ultimately the vehicles maximum speed isreached at point of Figure 10 or at 2500 r.p.m. in lFigure 7.

As is evident from the speed chart (Figure 12) the points 119 and 115,likewise the points 116 and 120 of Figure 11, do not lie exactly one ontop of the other but at approximately 25 revolutions of the drive-offshaft away from each other. This diierence is necessary in order toensure a faultless operation of the hydraulic units A and B rightthrough their neutral positions.

In a precisely contrary manner, the speed reduction takes place byturning back Ithe controller cylinders 42, 43, 54 and 55 by means of thehand crank 53.

We claim:

1. An innitely variable transmission comprising a rotatable drivingshaft, a rotatable driven shaft coaxial with the driving shaft,supporting means attached to the driven shaft, a plurality of planetarygear systems each containing a respective set of identical planet gearwheels rotatably mounted in said supporting means, toothed gearing rigidwith the input shaft and operatively connected to said planetary gearwheels, two hydraulic units each adapted to operate as a pump and alsoadapted to operate as a motor, ducts providing intercommunicationbetween the hydraulic units, rotatable controller cylinders mechanicallyconnected to the hydraulic units and adapted to change each of saidunits over from operation as a pump to operation as a motor and viceversa, and coupling devices adapted to mechanically couple each of saidhydraulic units to a respective one of said systems, whereby during theoperation of the transmission mechanism power can be transmitted fromthe driving shaft to the driven shaft partly through the hydraulic unitsand partly mechanically and independently of the hydraulic units, andthe axes of rotation of the planet gear wheels rotate about the commonaxis of the driving and driven shafts.

2. A transmission mechanism as claimed in claim l, said supporting meanscomprising a casing rigid with the driven shaft and enclosing the planetgear wheels, internal teeth on said casing, a casing drive pinionmounted for rotation about a iixed axis and meshing with said internalteeth, a first rotary power transmission shaft projecting from one ofthe hydraulic units and adapted to be coupled to said casing drivepinion, internal bearings in said casing, planet wheel spindlesrotatably mounted in said bearings, planet gear driving pinions eachrigid with a respective one of said spindles, said toothed gearingincluding an input pinion rigid with the driving shaft and meshing witheach of the planet gear driving pin-ions, a first set of said identicalplanet gear wheels each rigid with a respective one of said spindles, asecond rotary power transmission shaft projecting from the otherhydraulic unit, a first hollow shaft rotatable coaxially with thedriving shaft and having an end which projects from the casing and isadapted to be coupled to the second rotary power transmission shaft, afirst central pinion rigid with the Iirst hollow shaft and meshing witheach and adaptedotqbe wupledntothe Sefmdsrotary Power transmissionIshaftL a central/gear wheel rigid with the the second Setofplanet gearwheels, @third semi-identi- `cal planet gearWheelsrotatablyysupported-ig the casing,

a third hollow shaft` rotatable coexielrlyvwith Vthevdriving shaftanlvvhavinggan epd whichv projects from the easing and is adapted tobeVcoupled 'to theirsg power transmission shaft, a; secondVY central`pinionrigilwith-'the third 8. hollqwf Shaft A@1114.1v @shine with auchwheel, of the third set of planet gear wheels, said toothedgearingyfilrther,

inluding. an?innutlfeearrwheelxgidwithi116- drvingfshaft andmeshing-with thfthirdzset 1 Qf. planertlgear wheels.

Vl'lefer'eilces ,Ctedz in the lerof thispAatent UNITED-STATES PATENTS'

